Machine for producing tubular products with a cutter carried by a rotating arm and relative production method

ABSTRACT

The machine comprises a mandrel ( 4 ), a winding member ( 7 ) to helically wind said strips of web material about said mandrel and form a continuous tube; and rotating disk-shaped cutter ( 25 ), cooperating with said mandrel ( 4 ), to cut the continuous tube (T) into individual tubular products (M). The disk-shaped cutter ( 25 ) is carried by a rotating arm ( 23 ).

TECHNICAL FIELD

The present invention relates to a corewinder, that is, a machine ordevice used to produce tubular products from strips of web materialwound helically about a mandrel and glued to form the finished product.

The invention also relates to a method for producing tubular products ofthe aforesaid type.

STATE OF THE ART

In the production of rolls of web material, for example rolls of toiletpaper, rolls of kitchen towel, rolls of non-woven fabric, rolls ofadhesive tape, plastic film, metalized film or the like, tubes ofcardboard or another material are commonly utilized as winding cores,obtained by overlapped and staggered winding of at least two strips ofweb material bonded together. Winding is performed by machines calledcorewinders, which have a forming mandrel (fixed or supported idle aboutits axis) about which strips of web material previously provided with alayer of glue are wound. In practice, the glue is applied to one of thetwo faces of every strip except one. Winding is obtained by means of awinding member, typically a continuous belt, which forms a helical turnabout the mandrel and causes the strips of web material to be drawn andwound, and also exerts the pressure required for bonding.

Examples of machines of this type are described in U.S. Pat. Nos.3,150,575; 3,220,320; 3,636,827; 3,942,418; 4,378,966; 4,370,140;5,468,207; 5,873,806.

The strips of web material are wound continuously and form a continuoustube which is then cut into sections of the required length by means ofcutting members disposed along the extension of the forming mandrel orat the end thereof. Devices of various types have been produced to cutthe continuous tube into individual sections. These must be reliable,perform accurate cutting and allow high production speeds to be reached.The U.S. Pat. No. 5,873,806 relates in particular to a cutting devicefor corewinders, wherein a pair of rotating cutters are brought intocontact with pressure against the tube to be cut or, alternatively,withdrawn. When in the cutting position they are made to advance at thesame speed as the tube being formed and a particular kinematic system isused to rotate the cutters taking motion from the same motion as thecarriage carrying the cutters, which translates forwards and backwards.

This cutting device is particularly efficient and allows considerableproduction speeds to be reached. Nonetheless, it is complex andrelatively expensive. Moreover, it does not allow high speeds to bereached due to the inertial forces and the vibrations produced as aresult of the alternate motion supplied to the carriage carrying thecutters.

OBJECTS AND SUMMARY OF THE INVENTION

The object of the present invention is to produce a machine to producetubular products, with a cutting device of the continuous tube beingformed that is economical and reliable and that improves the performanceof the machine.

The object of a preferred embodiment of the present invention is toproduce a machine wherein the cutting device does not have the problemsderiving from the inertial stresses produced by the alternate movements.

Essentially, according to the invention a machine to produce tubularproducts through helically winding strips of web material (so calledcorewinder), is provided with a disk-shaped cutter carried by a rotatingarm, which makes the cutter follow a trajectory that interferes with thetube being formed around the mandrel of the machine, so that during aportion of the rotatory travel of the arm the cutter cuts the tube.

Within the scope of the present description and of the appended claims,the disk-shaped cutter is understood to be any disk-shaped member thatacts on the cardboard to produce the cut. This may be an actual cutter,with a smooth or preferably serrated cutting edge. Nonetheless, it mayalso be a grinding wheel or an abrasive disk, which in this contextcarries out the function of a cutter.

In the present description and in the appended claims, unless otherwisespecified, rotatory motion is intended both as a movement always in thesame direction of rotation, without reversal, and as an alternate oroscillating rotatory motion, that is, with reversal of the direction ofrotation. Analogously, unless otherwise specified, rotating arm must begenerically intended as an arm rotating always in the same direction, oralso as a mobile arm with alternate, that is oscillating, rotatorymotion.

The rotatory motion always in the same direction and preferablycontinuous, that is without stops, makes it possible to obtain thefurther advantage of decreasing stresses to eliminate or greatly reducethe inertial forces and resulting vibrations in the machine.

Thanks to the limited number of elements and moving parts, the cuttingdevice is particularly simple.

When movement is rotatory without reversal of the direction of rotation,it is generally continuous, although not at constant speed. This allowsthe machine to be adapted to different lengths of the tubular product tobe produced. Indeed, the arm is made to rotate so that the advance speedof the cutter is essentially approximately equal to the advance speed ofthe tube being formed around the mandrel for the time during which thecutter is engaged in the tube to be cut. During the remaining part ofrotation the arm may be accelerated or decelerated (even stoppedbriefly) to allow the tubular material being formed to advance for therequired length between one cut and the next.

According to a particularly advantageous embodiment of the invention thearm carrying the cutter rotates about an axis that is skew with respectto the axis of the mandrel around which the strips forming the tubularproduct are wound and positioned at 900 with respect thereto.

Although in theory it is possible also to provide more than one rotationarm and more than one cutter, to obtain a particularly simple machine,it is advantageous to use a single arm with a single cutter. In thiscase the trajectory of the cutter with respect to the continuous tubeformed about the mandrel is such that the cutter engages the tube for anarc of rotation of the arm, during which the tube performs at least onecomplete rotation about the axis of the mandrel. In this way a singlecutter performs the entire cut of the tube.

As shall be explained hereunder, with reference to the examples ofembodiment, the cutter may be carried by the rotating arm so that itassumes with its axis a fixed position with respect to the arm. In thiscase the axis of the disk-shaped cutter will not be exactly parallel tothe axis of the mandrel and therefore of the tube to be cut for theentire cutting arc. Nonetheless, if the arm carrying the cutter issufficiently long, the variation in the direction of the axis ofrotation of the cutter with respect to the axis of the mandrel islimited and acceptable. In particular, it is possible for this variationto be no greater than +/−8-10°. In a slightly more complex although moreaccurate embodiment, the cutter may assume a variable position withrespect to the rotating arm carrying it, so that its axis of rotationremains parallel to the axis of the mandrel for the entire time or forthe majority of the time during which the cutter is in contact with thetube to be cut. Alternatively, the position of the mandrel may becontrolled to reduce the error in parallelism between the axes withoutnecessarily providing an accurate parallelism.

For this purpose it is possible, for example, for the cutter to becarried by a support oscillating or rotating about an axis carried bythe rotating arm and parallel to the axis of rotation of said arm.

In principle, the cutter may be supported idle about its axis, and maybe drawn by friction with the material forming the tube to be cut.Nonetheless, to obtain a more reliable cut it is preferable for thecutter to be motorized, for example by means of a pneumatic motor, whichmay be fed with compressed air supplied to the rotating arm by means ofa rotating distributor. The cutter may have a smooth circular blade.Nonetheless, in a preferred embodiment, the cutting edge of the cutteris toothed or serrated. In this case it may be advantageous to provide asystem for suction of the shavings or dusts which are formed during thecut.

Further advantageous characteristics and embodiments of the machineaccording to the invention shall be described hereunder and areindicated in the appended dependent claims.

According to a different aspect, the invention relates to a method forproducing tubular products, wherein:

-   -   strips of web material are wound helically about a winding        mandrel, to form a tube in continuous mode;    -   the tube is divided into sections to form said tubular products,        by means of at least one rotating disk-shaped cutter that comes        into contact with said tube and advances with it along the        mandrel during the cut.

Characteristically, according to the invention, the cutter is made toadvance along the path of the tube to be cut by making it rotate on arotating arm about an axis not parallel to the axis of the mandrel.

Further advantageous characteristics of the method according to theinvention shall be described hereunder and are indicated in thedependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention shall be better understood with reference to thedescription hereunder and to the accompanying drawings, showing anon-limiting practical embodiment of the invention. In the drawing,where equivalent or corresponding parts are indicated with the samereference numerals:

FIG. 1 shows a side view of a corewinder according to the invention in afirst embodiment;

FIG. 2 shows an enlarged detail of the cutting area of the tube; and

FIG. 3 shows a side view of a corewinder in a second embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows as a whole a possible embodiment of a corewinder to whichthe present invention is applied. It must however be understood that theinvention may also be applied to machines with a different structure, aslong as they are provided with a forming mandrel to form tubes, whichmay be fixed or rotating about its axis, and which require a cuttingdevice to cut the tube formed continuously about the mandrel intosections or tubular products.

Briefly, and limited to the parts of interest for the presentdescription, the machine in FIG. 1, indicated as a whole by 1, comprisesa load-bearing structure 3 from which a mandrel 4 is supported in acantilever fashion, a first end thereof being constrained to theload-bearing structure 3 by means of a sleeve 8. The opposite end of themandrel 4 terminates in proximity to the area in which the tube is cut.A conveyor belt 10 or the like then removes the individual tubularproducts obtained from cutting a tube T, formed continuously asdescribed hereunder about the mandrel 4.

To form the tube T, continuous strips of cardboard or of anothercontinuous web material are fed to the corewinder 1. In the exampleshown two strips indicated with S1 and S2 are employed. These are woundhelically about the mandrel 4 with the aid of a continuous belt 7 whichhas two branches 7A and 7B, driven about two pulleys 9 and 17, of which9A and 17A indicate the respective axes of rotation. The branch 7A formsa helical turn about the mandrel 4 and about the strips of web materialS1 and S2 being wound. The numeral 19 indicates the motor which drawsthe driving pulley 17 in rotation, causing movement of the belt 7.

Inclination of the assembly formed of the pulleys 9, 17, of the belt 7and of the motor 19 is adjustable by means of a threaded bar 20 and ahandwheel 22, so as to adjust inclination of the helical turns formed bythe two strips S1, S2 about the axis of the mandrel 4.

The two strips S1 and S2 are wound overlapping and staggered, so that ahelix formed by the turns of the outermost strip S1 overlaps, forexample, by being staggered by half a pitch, a helix formed by the turnsof the innermost strip S2.

A glue is applied to the inner surface of the outer strip S1 and/or tothe outer surface of the inner strip S2 in a way per se known and notshown, to make the two turns adhere to each other.

The tube T is produced continuously and must therefore be cut intosections of the required length. For this purpose, a cutting device,indicated as a whole with 21, is provided downstream of the windingsystem 7, 9, 17, 19 with respect to the direction of feed fT of the tubealong the forming mandrel 4.

The cutting device 21, shown in detail also in FIG. 2, comprises an arm23 rotating about an axis B positioned at 90° with respect to the axis Aof the mandrel 4 and skew with respect thereto. The direction ofrotation (clockwise in the drawing) of the arm 23 is indicated with f23.At the distal end, that is the end away from the axis of rotation B, thearm 23 carries a disk-shaped cutter 25 motorized by a motor 27. In theexample shown the motor 27 is a pneumatic motor, fed by a compressed airduct, indicated schematically with 29, which receives the compressed airthrough a rotating distributor, not shown in detail.

In the Figure the cutting device 21 is located under the mandrel 4.Nonetheless, it must be understood that it may be located in anysuitable position with respect to the axis of the mandrel, also as afunction of the requirements for space.

The cutter 25 rotates about its axis D (FIG. 2) which, in the example inFIGS. 1 and 2, assumes a fixed position with respect to the arm 25. Inthis way when the arm 25 rotates about the axis B, the point of theblade of the cutter 25 farthermost from the axis of rotation B of thearm 25 travels along a circumference C that intersects in two points theexternal surface of the tube T being formed on the mandrel 4, as can beseen in particular in FIG. 2. For the entire arc of rotation of the arm25 between the positions corresponding to the points of intersectionbetween the circumference C and the cylindrical surface of the tube Tthe cutter 25 is in contact with said tube and performs cutting.

In FIG. 2 the arm 23 is shown in the angular position corresponding tothe start of cutting of the tube T, that is in the first positionwherein the circumference C intersects the cylindrical surface of thetube T. The position of the cutter in the point wherein thecircumference C intersects the cylindrical outer surface of the tube Tfor the second time is shown with 25X. After moving beyond this positionthe cutter 25 is no longer in contact with the tube.

Complete cutting of the tube T must be performed between these twopositions of the cutter to obtain the single section or final tubularproduct M, which is removed by the conveyor 10. To obtain completecutting, the tube T must carry out a complete rotation about its axisduring the time wherein the cutter 25 is in contact with it. In actualfact, not all the arc of rotation between the two end positions of thecutter shown in FIG. 2 is available for cutting. In fact, to obtaincomplete cutting a complete rotation of the tube must take place withthe cutter inserted in the material forming the tube T for the entirethickness thereof. Therefore, the tube T will perform a rotationexceeding 360° while the cutter 25 will pass from one to the other ofthe positions shown in FIG. 2.

To allow the cutter to penetrate the cylindrical wall forming the tube Twithout deforming said tube it may be suitable for the mandrel 4 toextend inside the tube in the area of action of the cutter, as shown inFIG. 2, although in principle a shorter mandrel 4, which does not reachthe cutting area, may be used. This can, for example, be provided whenthe material of the tube is sufficiently stiff and/or when themechanical characteristics of the cutter allow easy penetration in saidmaterial.

In the example shown, the mandrel 4 is provided with a decreased area atthe level of the area of action of the cutter, that is, a portion inwhich the cross section of the mandrel is smaller with respect to theinternal section of the tube. For example, the mandrel may be providedwith a ground part on the side from which the cutter penetrates thematerial. In this case the mandrel must not be rotating. Alternatively,as shown in the drawing, the mandrel may have a circular section with asmaller diameter. This solution may be adopted both with a rotatingmandrel and with a fixed mandrel.

The tubular product M obtained from the cut performed by the cutter 25is removed by the conveyor 10, through the effect of the speed of saidconveyor, which is greater than the speed at which the tube T is formed.

To contrast the stress of the cutter 25 during cutting, as shown in theexample in the drawing, a rest 28 may be provided, constituted by a pairof idle rollers, inclined by an angle approximately equal to the angleof the helix formed by the strips S1, S2, and acting on the tube T onthe opposite side with respect to the cutter 25.

If the cutter 25 has a toothed or serrated blade, as will be preferableto obtain a more efficient cut, it is advisable to provide a suctionoutlet or another means to remove dusts and shavings in the cuttingarea. This is schematically indicated in FIG. 2 with a dashed line 30.The outlet has an elongated form so that suction is performed along theentire area of action of the cutter 25. More than one outlet can beprovided, for example also on two sides of the mandrel 4.

As is shown in FIG. 2, as the cutter 25 is carried with its axis ofrotation D in a fixed position with respect to the arm 25, the planeidentified by its edge will not always be orthogonal to the axis of themandrel 4. To correct this defect in parallelism between the axis D andthe axis A, the cutter 25 may be mounted on a support oscillating orrotating on the arm 23, in a way coordinated with the rotationalmovement of said arm. For this purpose an actuator may be mounted on thearm 23 to actuate a support of the cutter 25 oscillating around an axisparallel to the axis B. Otherwise, as shown in the example in FIG. 3, asupport 31 rotating about an axis E carried by the arm 23 and parallelto the axis B may be provided. Integral with the support 31 is a toothedwheel 33 coaxial with the axis D, around which a toothed belt 35 runs,which in turn runs around a second fixed toothed wheel 37 coaxial withthe axis B of rotation of the arm 23. In this way when the arm 23rotates about the axis B, as well as rotating about the axis D (cuttingmotion) the cutter 25 also moves in space according to a trajectory thatis the combination of the motion about the axis B and about the axis E.By choosing the dimension of the various mechanical membersappropriately the axis D of the cutter may be maintained parallel withrespect to the axis A of the mandrel during cutting. If the pulleys 33and 37 have the same diameter, the axis D remains parallel to the axis Aof the mandrel 4 at all times.

When the motion of the support 31 about the axis E is supplied by anindependent actuator, the arm 23 may be provided with a rotationalmotion that is not a continuous rotational motion, but an alternaterotational motion, as the cutter 25 may be taken to the reversedposition during the return travel to prevent interference with the tubebeing formed. If the motion is continuous, or in any case always in thesame direction, as mentioned hereinbefore it is possible to modulate theangular speed of the arm 23, to obtain the desired length of individualproducts M produced from cutting the tube T. In fact, to obtain this therotation speed of the arm may be decreased or increased when the cutteris not operating.

Moreover, to adapt the machine to different diameters of the mandrel 4and therefore of the tube T being formed, the distance between the axisA of the mandrel 4 and the axis B of rotation of the arm 23 mayadvantageously be adjustable.

It is understood that the drawing merely shows a practical embodiment ofthe invention, which may vary in forms and layouts without howeverdeparting from the scope of the concept on which the invention is based.Any reference numerals in the appended claims are provided purely tofacilitate reading in the light of the description hereinbefore and ofthe accompanying drawings, and do not limit the scope of protectionwhatsoever.

1. A machine for producing tubular products by means of helical windingof strips (S1, S2) of web material, comprising a mandrel (4), a windingmember (7) to helically wind said strips of web material about saidmandrel and form a continuous tube; and a rotating disk-shaped cutter(25), cooperating with said mandrel (4), to cut the continuous tube (T)into individual tubular products (M), characterized in that saiddisk-shaped cutter (25) is carried by a rotating arm (23).
 2. Machine asclaimed in claim 1, characterized in that said arm (23) is rotatingabout an axis (B) positioned at 90° with respect to the axis (A) of themandrel (4) and skew with respect thereto.
 3. Machine as claimed inclaim 1 or 2, characterized in that said arm (23) always rotates in thesame direction.
 4. Machine as claimed in claim 1, 2 or 3, characterizedin that the rotation speed of said arm is controlled so that the advancespeed of the cutter is approximately equal to the advance speed of thecontinuous tube (T) along said mandrel (4) during cutting.
 5. Machine asclaimed in claim 3 or 4, characterized in that the rotation speed of thearm (23) is adjustable as a function of the length of the tubularproducts (M) to be cut.
 6. Machine as claimed in one or more of theprevious claims, characterized in that the trajectory of the cutter withrespect to the continuous tube (T) formed about said mandrel is suchthat the cutter engages the tube for an arc of rotation of the arm,during which the tube performs at least one complete rotation about theaxis of the mandrel.
 7. Machine as claimed in claim 6, characterized inthat while the cutter (25) is in contact with the tube being formedabout the mandrel, its axis of rotation (D) is maintained approximatelyparallel to the axis (A) of the mandrel (4).
 8. Machine as claimed inclaim 6, characterized in that while the cutter (25) is in contact withthe tube (T) being formed about the mandrel, its axis of rotation (D)forms an angle no greater than 10° with the axis (A) of the mandrel (4).9. Machine as claimed in one or more of the previous claims,characterized in that said cutter (25) is motorized.
 10. Machine asclaimed in claim 9, characterized in that said cutter is motorized bymeans of a pneumatic motor (27).
 11. Machine as claimed in one or moreof claims 1-6 and 8-10, characterized in that the axis of rotation (D)of said cutter (25) is essentially fixed with respect to the rotatingarm (23).
 12. Machine as claimed in one or more of claims 14 and 9-10,characterized in that the axis of rotation (D) of the cutter (25) isoscillating or rotating with respect to said arm (23), so that while thecutter is engaged in the tube (T) its axis of rotation (D) is maintainedessentially parallel to the axis (A) of the mandrel (4).
 13. Machine asclaimed in claim 12, characterized in that the cutter (25) is carried bya support (31) rotating about an axis (E) essentially parallel to theaxis of rotation (B) of said arm (23).
 14. Machine as claimed in one ormore of the previous claims, characterized by a support (28) for themandrel, to supply a reaction force against the stress applied by saidcutter on said mandrel.
 15. Machine as claimed in one or more of theprevious claims, characterized in that said cutter (25) has a toothedcutting edge.
 16. Machine as claimed in claim 15, characterized in thata suction member (30) is associated with said cutter (25) to eliminatedebris formed during cutting.
 17. Machine as claimed in one or more ofthe previous claims, characterized in that said mandrel (4) has an areawith a decreased cross section, at the level of the portion wherein saidcutter is in contact with the tube being formed about said mandrel. 18.Machine as claimed in one or more of the previous claims, characterizedin that said rotating arm rotates about an axis (B), the distance ofwhich with respect to the axis (A) of the mandrel is adjustable.
 19. Amethod for producing tubular products, wherein: strips (S1, S2) of webmaterial are wound helically about a winding mandrel (4), to form a tube(T) in continuous mode; the tube is divided into sections to form saidtubular products, by means of at least one rotating disk-shaped cutter(25) that comes into contact with said tube and advances with it alongthe mandrel during the cut. characterized in that the cutter is advancedby making it rotate with a rotating arm about an axis (B) not parallelto the axis of the mandrel.
 20. Method as claimed in claim 19,characterized in that said arm (23) rotates always in the samedirection.
 21. Method as claimed in claim 19 or 20, characterized inthat the rotation speed of said arm is controlled so that the advancespeed of the cutter is approximately equal to the advance speed of thecontinuous tube (T) along said mandrel (4) during cutting.
 22. Machineas claimed in claim 20 or 21, characterized in that the rotation speedof the arm (23) is adjustable as a function of the length of the tubularproducts (M) to be cut.
 23. Method as claimed in one or more of claims19 to 22, characterized in that said arm rotates about an axispositioned at 900 with respect to the axis of the mandrel and skew withrespect thereto.
 24. Method as claimed in one or more of claims 19 to23, characterized in that said cutter is motorized.
 25. Method asclaimed in one or more of claims 19 to 24, characterized in that theaxis of rotation of said cutter maintains a fixed position with respectto said rotating arm.
 26. Method as claimed in one or more of claims 19to 24, characterized in that inclination of the axis of rotation of thecutter with respect to said arm is controlled, to maintain the axis ofrotation of the cutter essentially parallel to the axis of the mandrelduring cutting.